Field of the Invention
The invention relates to a communication system, and more particularly, to an audio communication system.
Description of the Related Art
In an audio communication system, high-frequency signals (e.g. >15.8 KHz) are used to transmit data, wherein the high-frequency signals are difficult to identify by the human ear. In general, the audio signal may be a single tone signal or a multi-tone signal. Therefore, a receiving apparatus can obtain data or instructions from a transmitting apparatus by detecting the tones (i.e. frequencies) of the audio signals.
However, an audio signal will be reflected by the obstacles in the environment when an audio signal is transmitting, such that a time difference between the reflected signal and the audio signal will be generated when the signals arrive at the receiving apparatus, thereby causing interference. For example, the receiving apparatus may simultaneously receive the audio signals transmitted at different time, so that the receiving apparatus can not identify the received audio signals. Thus, a detection-accuracy rate is decreased. Traditionally, the reflecting power of the previous audio signals is attenuated by adding a period of silence between two adjacent audio signals so as to avoid interference of the current audio signal. However, the added silence will extend the total time needed for data transfer, and thus the data-transmission rate is decreased.